High-capacity uranium extraction from seawater through constructing synergistic multiple dynamic bonds in confined spaces

Abstract

Seawater is the largest uranium reserve in the world, and the efficient extraction of uranium from seawater facilitates the sustainable development of the nuclear industry for thousands of years. However, conventional extraction processes must suffer the dissociation of CO32− ions from [UO2(CO3)3]4− anions to bind the uranyl core, which has a high energy barrier, resulting in the poor selectivity and long working times. Here, we combine a molecular templating strategy to synthesize five hydroxy-rich covalent organic frameworks (COFs) with tunable nanopore sizes (from 0.6 to 2.5 nm). In the 1.1-nm-sized COF cavity, hydroxyl groups coupled with the hydrogen-bonded NH4+ cations selectively bind uranyl tricarbonate ions via synergistic electrostatic and hydrogen-bonding interactions. This framework exhibits high uranium-extraction capability with a removal ratio of >99.99 % in 400 min. Notably, a record uranium-adsorption uptake is achieved with a capacity of 23.68 mg g−1 in 7 days from natural seawater, surpassing that of classical amidoxime-based adsorbents by a factor of 350%.